This is the catalytic region of aspzincins, a group of lysine-specific metallo-endopeptidases in the MEROPS:M35 family. They exhibit the following active-site architecture. The active site is composed of two helices and a loop region and includes the HExxH and GTxDxxYG motifs. In UniProt:P81054, His117, His121 and Asp130 coordinate to the catalytic zinc ligands. An electrostatically negative region composed of Asp154 and Glu157 attracts a positively charged Lys side chain of a substrate in a specific manner [4].

1: Kinetic characterization of lysine-specific metalloendopeptidases from Grifola frondosa and Pleurotus ostreatus fruiting bodies. Nonaka T, Hashimoto Y, Takio K; J Biochem. 1998;124:157-162. PMID:9644258

2: The lysine-specific proteinase from Armillaria mellea is a member of a novel class of metalloendopeptidases located in Basidiomycetes. Healy V, O'Connell J, McCarthy TV, Doonan S; Biochem Biophys Res Commun. 1999;262:60-63. PMID:10448068

3: Structure of a new 'aspzincin' metalloendopeptidase from Grifola frondosa: implications for the catalytic mechanism and substrate specificity based on several different crystal forms. Hori T, Kumasaka\t\t T, Yamamoto M, Nonaka N, Tanaka N, Hashimoto\t Y, Ueki U, Takio\t K; Acta Crystallogr D Biol Crystallogr. 2001;57:361-368. PMID:11223512

4: A quick solution: ab initio structure determination of a 19 kDa metalloproteinase using ACORN. McAuley KE, Jia-Xing Y, Dodson EJ, Lehmbeck J, Ostergaard PR, Wilson KS; Acta Crystallogr D Biol Crystallogr. 2001;57:1571-1578. PMID:11679721